Inhibition of neurogenic and thromboxane A 2 ‐induced human prostate smooth muscle contraction by the integrin α2β1 inhibitor BTT‐3033 and the integrin‐linked kinase inhibitor Cpd22

Introduction Prostate smooth muscle contraction is critical for etiology and treatment of lower urinary tract symptoms in benign prostatic hyperplasia (BPH). Integrins connect the cytoskeleton to membranes and cells to extracellular matrix, what is essential for force generation in smooth muscle contraction. Integrins are composed of different subunits and may cooperate with integrin‐linked kinase (ILK). Here, we examined effects of inhibitors for different integrin heterodimers and ILK on contraction of human prostate tissues. Methods Prostate tissues were obtained from radical prostatectomy. Integrins and ILK were detected by Western blot, real‐time polymerase chain reaction (RT‐PCR), and double fluorescence staining. Smooth muscle contractions of prostate strips were studied in an organ bath. Contractions were compared after application of solvent (controls), the ILK inhibitor Cpd22 ( N ‐methyl‐3‐(1‐(4‐(piperazin‐1‐yl)phenyl)‐5‐(4'‐(trifluoromethyl)‐[1,1'‐biphenyl]‐4‐yl)‐1H‐pyrazol‐3‐yl)propanamide), the integrin α2β1 inhibitor BTT‐3033 (1‐(4‐fluorophenyl)‐ N ‐methyl‐ N ‐[4[[(phenylamino)carbonyl]amino]phenyl]‐1H‐pyrazole‐4‐sulfonamide), or the integrin α4β1/α9β1 inhibitor BOP ( N ‐(benzenesulfonyl)‐ l ‐prolyl‐ l ‐O‐(1‐pyrrolidinylcarbonyl)tyrosine sodium salt). Results Western blot analyses of prostate tissues using antibodies raised against integrins α2b, α4, α9, β1, and ILK revealed bands matching the expected sizes of corresponding antigens. Expression of integrins and ILK was confirmed by RT‐PCR. Individual variations of expression levels occurred independently from divergent degree of BPH, reflected by different contents of prostate‐specific antigen. Double fluorescence staining of prostate sections using antibodies raised against integrins α2 and β1, or against ILK resulted in immunoreactivity colocalizing with calponin, suggesting localization in prostate smooth muscle cells. Electric field stimulation (EFS) induced frequency‐dependent contractions, which were inhibited by Cpd22 (3 µM) and ...